Fire Alarm -  In this fire alarm circuit project, a thermistor works as the heat sensor.  When temperature increases, its resistance decreases, and vice versa.  At normal temperature, the resistance of the thermistor (TH1) is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature ncreases beyond 100°C.  The circuit uses __ Designed by Popescu Marian

Fire Alarm -  This circuit warns the user against fire accidents.  It relies on the smoke that is produced in the event of a fire.  When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases.  This causes the resistance of LDR to increase and the voltage at the base of the transistor  __  Designed by Radioland.nt.au

Make a Fire-alarm System for Your House! -  Many buildings and homes need smoke detectors to alarm at the initial stage of a developing fire accident.  To prevent damage, smoke detectors perform… __ Designed by Upasana Dewan

Photodiode-Based Fire Detector -  This ultra-sensitive fire sensor protects your electronic devices like computer and television set.  It uses a photodiode as the fire sensor and sounds an alarm immediately on sensing a spark or...___ Electronics Projects for You

Photoelectric Smoke Detector -  This photoelectric smoke detector circuit uses one LED and 2 LDRs to detect the smoke and sound an alarm.  The LM1801 IC is the best choice for this circuit because we need a few external components and is used in almost any smoke alarm.  The whole photoelectric smoke detector circuit is powered from the 220V mains supply.  D1 __ Designed by Popescu Marian

Pin Diode Based Fire Sensor -  This is an ultra-sensitive fire sensor that activates an alarm when it detects fire.  In this circuit, a sensitive PIN diode is used as a fire sensor for longer-range fire detection.  It detects visible light and infrared (IR) in the range of 430 nm – 1100 nm.  Visible light and IR from the fire activate the sensor to trigger the alarm.  It also detects sparks in the mains wiring and if these persist, it gives a warning alarm.  The anode can easily be identified from the top-view flat surface of the photodiode.  A small solder point to which a thin wire is connected is the anode and the other one is the cathode terminal.___ Electronics Projects for You

Simple  Smoke Detector -  This simple smoke detector is highly sensitive but inexpensive.  It uses a Darlington-pair amplifier employing two npn transistors and an infrared photo-interrupter module as the sensor.  The circuit gives audio-visual alarm...___ Electronics Projects for You

Smart Smoke Alarm -  At the heart of this ultra simple smoke alarm is H21A1, which is a photo-interrupter module consists of a gallium-arsenide infrared LED coupled to a silicon phototransistor in a plastic housing.  The slot between the infrared sender(LED) and receiver (phototransistor) allows interruption of the signal with smoke, switching the __ Designed by T.K. Hareendran

Smoke Alarm -  The original smoke alarm circuit http://www.  electroschematics.  com/5450/smart-smoke-sensor-alarm/ has some problems and has left some hobbyists and students disappointed.  Rather than to attempt to solve its many problems, I have created an update that uses the venerable LM741 op amp.  It is simpler, more conventional, easier to __ Designed by Jim Keith

Smoke Detector -  This home smoke detector circuit warns the user against fire accidents.  It relies on the smoke that is produced in the event of a fire and passes between a bulb and an LDR, the amount of light falling on the LDR decreases.  This type of circuit is called optical smoke detector.  Do not use it as a home smoke detector it’s __ Designed by Popescu Marian

Smoke, Alcohol & LPG-Detection Alarm Presented here is a circuit for raising an alarm on detecting smoke or LPG cooking gas leakage, or even alcohol vapours in breath.  This is achieved by using a basic unit...___ Electronics Projects for You

Fire Alarms Circuits